Tools, such as chisels and moil points, have long been used in demolition to break up concrete and the like. Hammer tools have been commonly used in conjunction with boom mountable power hammers for demolishing concrete because the hammer head has a larger striking face that can break up more concrete at each strike, or impact, than a traditional chisel or moil point. FIG. 1 shows the typical prior art hammer tool, or bit, 2 having an elongated body 4 with a shank 6 at one end and a hammer head 8 at the other end of the body 4. The hammer head 8 has a large, flat, circular striking face 10 in which to break up a work surface 12, such as concrete and the like.
In use, the shank 6 of hammer tool 2 is received into a power hammer 14, (shown in phantom). Much of the body 4, as well as the hammer head 8, extends externally and downwardly of power hammer 14. The power hammer 14 is raised and lowered over the work surface 12, in order to bring hammer head 8 into striking contact with work surface 12, typically, in a force range of up to 15,000 ft.-lbs class.
When hammer head 8 makes striking contact with the work surface, the hammer head is subjected to very high stress from the impact. The flat striking face of the hammer head directs all of the resulting stress upward at the time of impact. Stress lines are shown in dashes on FIG. 1, which are generally perpendicular to that of the striking face 10. The resulting stress is born by the hammer head 8, and is not concentrated within the power hammer supported portion of hammer tool 2. Hence, these type hammer tools can sustain hairline fractures, which can quickly lead to catastrophic failure of hammer head 8, thereby rendering hammer tool 2 useless.
These type of hammer tools are expensive, typically costing several hundred or even thousands of dollars. These type of hammer tools are heavy, as well, weighing anywhere from 100 to 1500 lbs. If catastrophic failure occurs, costly delays may ensue as replacement hammer tools may not be readily available, especially if the demolition site is remote. Additionally, injury to workers or property, could result as a consequence of catastrophic failure.
Moreover, although not generally intended, the hammer tool striking face may not always strike the work surface in a perpendicular (non offset) manner, such as shown in FIG. 2. This situation may occur because the work surface is not perfectly horizontal, or it may be attributed to operator error. Stress in this circumstance is concentrated at one end of the hammer head and adjacent portion of the body, shown at "16". Early catastrophic failure of the hammer tool is likely to occur at the unsupported area of the stress concentration.